SLIDING FRICTION AND WEAR OF CERAMICS IN NEUTRAL, ACID AND BASIC AQUEOUS-SOLUTIONS

Self-mated sliding couples of SSi3N4, HIP-RBSi3N4, SSiC, SiSiC, MgO-ZrO2 and Al2O3 were tested in different aqueous solutions (H2O, NaOH, KOH, NH4OH, HNO3, H2SO4, H3PO4, CH3COOH, HCl, HClO4) under conditions of boundary or mixed lubrication. The friction and wear behaviour depended considerably on the composition of the ceramics, but the nature of the aqueous solutions was of minor importance. The best frictional behaviour was observed with couples of SSiC, with steady state friction coefficients of 0.05. The lowest wear coefficients were measured for couples of the two types of Si3N4, SSiC and Al2O3 with values of approximately 10(-7) mm3 Nm-1. If low friction and low wear are required, couples of SSiC seem to be the best choice in most aqueous solutions.